Simple and Cheap Headlight Reminder

In an age where driving with the headlamps on is a standard practice, the driver of an MG may sometimes be forced to extreme measures when the headlamps go out by themselves after the car is parked. The aggravation and stress created when one of our MGBs turns into a several thousand pound paperweight because the headlamps were not turned off is mostly due to a difficulty in remembering that an MG is decades old and has very few user-friendly accessories like a “headlamp on” chime. Also, the MGB we drive most has a complex “headlamps-on-when-the-engine-is-running” circuit that our other MGBs do not have: most of the time we do not even think about the headlamps.

A variety of systems that turn the headlamps on and off when the car is driven and then parked are possible. They have various advantages and disadvantages, the selection of which must be left to the driver. However, we did not want another involved project-all we needed was to be gently reminded that the headlamps were on when the ignition was off.

One solution is actually quite simple: connect a 12 VDC alarm from the headlamps to the ignition. One such combination is the red circuit that powers the taillights and the green circuit that powers the fuel gauge and temperature sender. Since both these are fused, no additional fuse is necessary.

For the simplest circuit to check out the idea, obtain a Radio Shack piezo buzzer with a low current draw of about 10 milliamperes or less (for example, 273-059 with a catalog price of $3.49) and connect the black wire from the buzzer to the green terminal and the red wire from the buzzer to the red terminal of the fuse block. Older MGBs with a 2-fuse block will have the red circuit fused separately and the red connection will have to be made to the red circuit auxiliary fuse.

With the headlamps off there is no power to the red circuit. The buzzer mentioned will only operate with the red wire of the buzzer connected to power and the black wire from the buzzer connected to ground in some manner, so having power on the green circuit when the ignition is “on” does not result in backward current flow from the green circuit through the buzzer to the taillight grounds. Also, having both red and green terminals “on” gives no voltage drop across the buzzer and there is no sound. However, when the taillights are “on” and the ignition is “off” power flows from the red terminal through the buzzer and to the green terminal which grounds through the fuel gauge and temperature sender: the buzzer sounds every time we forget to turn the headlamps off when the car is parked.